These studies are designed to establish the mechanism by which neurohumoral agents interact with and alter intestinal electrolyte transport. Emphasis will be placed on the mechanism by which endephalins stimulate sodium and chloride absorption in order to determine whether these agents have a physiological effect on ion transport. The importance of these studies relate to the anti-diarrheal effect of codeine, morphine and other opiate compounds. In addition, the interaction of neurohumoral agents with receptors on enterocytes will be explored to establish whether all agents have specific receptors on enterocytes or are active through intermediary agents that alter electrolyte transport.